Lubricating oils used under the severe conditions of gasoline and diesel engines are highly compounded particularly to provide neutralization of acids derived from the sulfur in the fuel and from the oxidation of hydrocarbons; dispersancy so as to maintain sludge-forming precursors dispersed in the oil; improved wear protection and oiliness properties; as well as enhancing other attributes of the oil.
The desirability of having a single additive providing multifunctional properties is evident in the efficiency and economics in the manufacturing and use of a single additive as compared to a plurality of additives. However, because of the severe operating conditions under which lubricants perform in internal combustion engines, it is frequently found that one additive, while effectively performing a particular function, will tend to cause another problem.
Sulfurized alkylphenols are well known in the lubricants art as precursors for making lubricating oil additives. More particularly, sulfurized alkylphenols are well known as precursors for neutral and overbased alkaline earth metal phenates. See, for example, U.S. Pat. Nos. 3,367,867, and 3,741,896. Similarly, the sulfurized alkylphenols have been used in many other reactions, for example, the reaction of a sulfurized phenol with a Mannich base, U.S. Pat. No. 3,741,896.
The sulfurized alkylphenols cannot themselves be used as a lubricating oil additive because of their corrosive effect on engine parts. This corrosiveness is believed to be due in part to the presence of free sulfur found in the product of the reaction of sulfur and phenol.